This invention relates to electronic image processing systems, especially though not exclusively for processing video signals representing a television picture.
Electronic image processing systems are known, capable of capturing video signals representing a television picture and processing these signals to produce the effect of three dimensional manipulation of the picture. One such system is the Encore system manufactured by Quantel Limited of Newbury, Berkshire, England. With this system it is possible to produce a 3D spin of the picture or change the position, size, or view position of the picture using manual controls which include a tracker ball. To produce these effects, a frame store is provided in which is written a frame of video signals to be processed, and a processing circuit responsive to signals set up by the manual controls determines successive addresses in the frame store from which the successive video signals should be read, to build up an output frame containing the processed picture. The system is interactive, inasmuch as the writing, processing and reading is repeated frame by frame, the input in each frame period, being formed by the output of the preceding frame period. A monitor is provided for displaying successive processed frames as a moving picture so that the operator can observe the effect of his manipulation of the controls in real time. During each frame period the processing circuit responds to the incremental control signals set up during the preceding frame. The processing circuit may for example be of the construction described in our British Patent No. B 2,073,988. (equivalent U.S. Pat. No. 4,437,121).
One use to which systems such as described in the preceding paragraph may be put is that of transforming a flat picture so that it can be placed exactly over a polygonal shape (usually quadrilateral) on another picture to build up a composite picture. For example the first picture may be a view through a window and it may be required to place the picture over the window seen from different positions. It is possible to achieve this result using the existing controls on the Encore equipment, but in practice it is a difficult and time consuming process as it may involve a combination of spin--and changes in size, position and point of view of the picture to be superimposed.
One early proposal for solving the above difficulties, attempted in-house by the assignee of this application, involved image processing equipment comprising means for defining the corner positions of a picture and means for transforming the addresses of the picture points of the picture to fit the picture over the quadrilateral defined by the corner positions, assuming a given viewpoint. In this in-house attempt, the transformation was carried out in one operation and was not interactive.
The object of the present invention is to provide an improved image processing system in which effects such as that described in the preceding paragraph can be more easily achieved.